The use of trunking to carry electrical cables is well known. Such trunking is commonly used in the pharmaceutical, food and beverage industries and in such circumstances it is of particular importance that the external surfaces of the trunking are easily cleaned. Typically such trunking may be provided with waterproof seals so that it may be cleaned by directing a jet of water at the trunking the seals preventing any of the water gaining access to the electrical cables inside.
An example of such a trunking system is shown in FIG. 1 in which trunking sections 10 and 12, having respective lids 14 and 16, are joined by a coupling 18. Trunking sections 10 and 12, lids 14 and 16 and coupling 18 are all formed by the pressing of sheet stainless steel. Coupling 18 is formed such that its external surfaces engage with the internal surfaces of trunking sections 10 and 12. Trunking sections 10 and 12 are also provided with holes 20 which are adapted to receive screws or other similar securing means (not shown) which in turn engage with holes 22 in coupling 18.
Trunking and coupling of this type have the disadvantage that it can be difficult to form a waterproof seal between the trunking sections 10 and 12 and coupling 18. For example, the number of screws which need to be inserted through apertures 20 and 22 make the installation process quite complex. Furthermore, this number of external fixings, each of which would typically have a slot or cross head, for engagement with a screw driver, are likely to attract dirt and are therefore provide potential infestation sites and make the cleaning process more difficult. This form of fixing also provides a direct route for ingress of water from the outside to the inside of the trunking where electrical cables are housed. For example, if a pressurised jet of water is directed onto the screws, it is possible for water to travel along the thread of the screw, under a capillary action, from the outside of trunking sections 10 and 12 to the inside of coupling 18.
A further problem found in trunking of this type is that the alignment of the trunking sections 10 and 12, coupling 18 and the screws inserted therein is of particular importance. The tolerance in the location of holes 20 and 22 must be very precise in order that the joining of the sections 10 and 12 is properly waterproofed. When screws are inserted into holes 20, 22 and are tightened it is possible for distortion of trunking sections 10 and 12 and coupling 18 to occur. This in turn causes the lid engaging edges 24 to not be correctly aligned. As a result, either lids 14 and 16 do not properly engage these edges 24 or the distortion of trunking sections 10 and 12 causes the ends of lids 14 and 16 to be incorrectly aligned with each other. This will further reduce the waterproof connection between the lids 14 and 16.
Preferred embodiments of the present invention seek to overcome the above described disadvantages of the prior art.